|Publication number||US5683615 A|
|Application number||US 08/664,035|
|Publication date||4 Nov 1997|
|Filing date||13 Jun 1996|
|Priority date||13 Jun 1996|
|Also published as||CA2257952A1, DE69731833D1, DE69731833T2, EP0904592A1, EP0904592B1, WO1997048110A1|
|Publication number||08664035, 664035, US 5683615 A, US 5683615A, US-A-5683615, US5683615 A, US5683615A|
|Inventors||Beth C. Munoz|
|Original Assignee||Lord Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (20), Non-Patent Citations (8), Referenced by (127), Classifications (5), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Y--((C)(R4)(R5))n --(O)w --
This invention relates to fluids that exhibit substantial increases in flow resistance when exposed to magnetic fields.
Fluid compositions that undergo a change in apparent viscosity in the presence of a magnetic field are commonly referred to as Bingham magnetic fluids or magnetorheological fluids. Magnetorheological fluids typically include magnetic-responsive particles dispersed or suspended in a carrier fluid. In the presence of a magnetic field, the magnetic-responsive particles become polarized and are thereby organized into chains of particles or particle fibrils within the carrier fluid. The chains of particles act to increase the apparent viscosity or flow resistance of the overall materials resulting in the development of a solid mass having a yield stress that must be exceeded to induce onset of flow of the magnetorheological fluid. The force required to exceed the yield stress is referred to as the "yield strength". In the absence of a magnetic field, the particles return to an unorganized or free state and the apparent viscosity or flow resistance of the overall materials is correspondingly reduced. Such absence of a magnetic field is referred to herein as the "off-state".
Magnetorheological fluids are useful in devices or systems for controlling vibration and/or noise. For example, magnetorheological fluids are useful in providing controllable forces acting upon a piston in linear devices such as dampers, mounts and similar devices. Magnetorheological fluids are also useful for providing controllable torque acting upon a rotary in rotary devices. Possible linear or rotary devices could be clutches, brakes, valves, dampers, mounts and similar devices. In these applications magnetorheological fluid can be subjected to shear forces, as high as 70 kPa, often significantly high, and shear rates in the order of 20,000 to 50,000 sec-1 causing extreme wear on the magnetic-responsive particles. As a result, the magnetorheological fluid thickens substantially over time leading to increasing off-state viscosity. The increasing off-state viscosity leads to an increase in off-state force experienced by the piston or rotor. This increase in off-state force hampers the freedom of movement of the piston or rotor at off-state conditions. In addition, it is desirable to maximize the ratio of on-state force to off-state force in order to maximize the controllability offered by the device. Since the on-state force is dependent upon the magnitude of the applied magnetic field, the on-state force should remain constant at any given applied magnetic field. If the off-state force increases over time because the off-state viscosity is increasing but the on-state force remains constant, the on-state/off-state ratio will decrease. This on-state/off-state ratio decrease results in undesirable minimization of the controllability offered by the device. A more durable magnetorheological fluid that does not thicken over an extended period of time, preferably over the life of the device that includes the fluid, would be very useful.
Magnetorheological fluids are described, for example, in U.S. Pat. No. 5,382,373 and published PCT International Patent Applications WO 94/10692, WO 94/10693 and WO 94/10694.
U.S. Pat. No. 5,271,858 relates to an electrorheological fluid that includes a carbon, glass, silicate, or ceramic particulate having an electrically conductive tin dioxide coating. The patent provides an extensive list of possible carrier fluids for the electrorheological fluid that includes esters and amides of an acid of phosphorus, hydrocarbon materials, silicates, silicones, ether compounds, polyphenyl thioether compounds, phenylmercaptobiphenyl compounds, mono- and di alkylthiophenes, chlorinated compounds and esters of polyhydric compounds.
U.S. Pat. No. 5,043,070 relates to an organic solvent extractant that includes an organic solvent extractant and magnetic particles, wherein the surface of the magnetic particles has been coated with a surfactant that renders the particles hydrophobic. The surfactant may be selected from ethers, alcohols, carboxylates, xanthates, dithiophosphates, phosphates, hydroxamates, sulfonates, sulphosuccinates, taurates, sulfates, amino acids or amines. Sodium dialkyl dithiophosphate and aryl dithiophosphoric acid are the only dithiophosphates mentioned in the extensive list of possible surfactants. There is no example, however, that includes a dithiophosphate.
U.S. Pat. No. 4,834,898 relates to an extracting reagent for magnetizing particles of nonmagnetic material that comprises water that includes magnetic particles having a 2 layer surfactant coating. The surfactant layers may be selected from ethers, alcohols, carboxylates, xanthates, dithiophosphates, phosphates, hydroxamates, sulfonates, sulphosuccinates, taurates, sulfates, amino acids or amines.
U.S. Pat. No. 4,253,886 relates to a method for preparing a ferromagnetic metal powder of particle size from 50-1000 angstroms. The particles are washed with a solution that contains (a) a volatile corrosion inhibitor; (b) (i) water, (ii) a water miscible organic solvent or (iii) a combination of (i) and (ii); and (c) an anionic surface active agent. Salt of a dithiophosphoric acid ester is mentioned as one of many possible types of surface active agents.
JP-B-89021202 relates to a magnetic powder that is iron or mainly iron that is surface treated with dialkyl dithiocarbamates of formula R1 R2 N--CS--S--R3 wherein R1 and R2 are alkyl and R3 is alkali metal or ammonium. The powder is used to formulate magnetic ink by mixing it with methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, vinylchloride/vinyl acetate copolymer, polyurethane resin, stearic acid, lecithin and a curing agent.
JP-A-62195729 relates to a magnetic lacquer for coating onto a substrate to make a recording medium. According to an English language abstract an example of the lacquer includes 100 parts by weight (pbw) Co-containing γ-Fe2 O3, 4 pbw α-Fe2 O3 powder, 4 pbw Mo-dithiocarbamate, 12 pbw nitrocellulose, 8 pbw polyurethane resin, 75 pbw cyclohexanone, 75 pbw toluene, 7.5 pbw methyl isobutyl ketone and 5 pbw polyisocyanate.
DD-A-296574 relates to a magnetic liquid that may includes magnetite monodomain particles with particle sizes of 5-20 nm. Zn dialkyldithiophosphide is included as a component at some stage in the production of the fluid, but it is not clear from an English language abstract what other components are present in a fluid with the Zn dialkyldithiophosphide.
None of these documents suggest any solution to the problem of providing a more durable magnetorheological fluid.
According to a first embodiment of the invention there is provided a magnetorheological fluid that includes magnetic-responsive particles, a carrier fluid and at least one thiophosphorus additive having a structure represented by formula A: ##STR1## wherein R1 and R2 each individually have a structure represented by:
Y--((C)(R4)(R5))n --(O)w --
wherein Y is hydrogen or a functional group--containing moiety such as an amino, amido, imido, carboxyl, hydroxyl, carbonyl, oxo or aryl;
n is an integer from 2 to 17 such that C(R4)(R5) is a divalent group having a structure such as a straight-chained aliphatic, branched aliphatic, heterocyclic, or aromatic ring;
R4 and R5 can each individually be hydrogen, alkyl or alkoxy; and
w is 0 or 1.
According to a second embodiment of the invention them is provided a magnetorheological fluid that includes magnetic-responsive particles, a carrier fluid and at least one thiocarbamate additive having a structure represented by formula B: ##STR2## wherein R1 and R2 each individually have a structure represented by:
wherein Y is hydrogen or a functional group--containing moiety such as an amino, amido, imido, carboxyl, hydroxyl, carbonyl, oxo or aryl;
n is an integer from 2 to 17 such that C(R4)(R5) is a divalent group having a structure such as a straight-chained aliphatic, branched aliphatic, heterocyclic, or aromatic ring; and
R4 and R5 can each individually be hydrogen, alkyl or alkoxy.
R3 of formula A or B can be a metal ion such as molybdenum, tin, antimony, lead, bismuth, nickel, iron, zinc, silver, cadmium or lead or a nonmetallic moiety such as hydrogen, a sulfur-containing group, alkyl, alkylaryl, arylalkyl, hydroxyalkyl, an oxy-containing group, amido or an amine. Subscripts a and b of formula A or B are each individually 0 or 1, provided a+b is at least equal to 1 and x of formula A or B is an integer from 1 to 5 depending upon the valence number of R3.
The magnetorheological fluids of the invention exhibit superior durability because of a substantial decrease in the thickening of the fluid over a period of use.
There also is provided according to the invention a magnetorheological device that includes a housing that contains the above-described magnetorheological fluids.
R1 and R2 of the thiophosphorus or thiocarbamate additive can be any group that imparts solubility with the carrier fluid. R1 and R2 preferably individually have the structure depicted previously for the thiophosphorus and thiocarbamate additives, respectively.
One possibility for R1 and/or R2 for both the thiophosphorus and thiocarbamate is an alkyl group. In general, any alkyl group should be suitable, but alkyls having from 2 to 17, particularly 3 to 16, carbon atoms are preferred. The alkyl could be branched if R4 and/or R5 are themselves alkyls or the alkyl could be straight-chained. Illustrative alkyl groups include methyl, ethyl, propyl, isopropyl, tert-butyl, pentyl, 2-ethylhexyl, dodecyl, decyl, hexadecyl, nonyl, octodecyl, and 2-methyl dodecyl.
Another possibility for R1 and/or R2 for both the thiophosphorus and thiocarbamate is an aryl group. In general, any aryl groups should be suitable. The aryl group can be directly bonded to the phosphorus atom of the thiophosphorus or it can be bonded via a divalent linking group such as an alkylene or an amido group. The aryl group can be bonded to the nitrogen atom of the of the thiocarbamate via a divalent linking group such as an alkylene or an amido group. Illustrative aryl-containing groups include phenyl, benzoyl and naphthyl. In general, any alkylaryl groups should be suitable. Illustrative alkylaryl groups include benzyl, phenylethyl, phenylpropyl and alkyl-substituted phenyl alcohol.
A further possibility for R1 and/or R2 for the thiophosphorus is an alkoxy group (in other words, subscript w is 1). In general, any alkoxy should be suitable, but alkoxy groups having from 2 to 17, preferably 3 to 16, carbon atoms are preferred. Illustrative alkoxy groups include methoxy, ethoxy, propoxy, and butoxy.
If Y is an amino group, possible R1 and/or R2 groups for the thiophosphorus and thiocarbamate include butylamine, nonylamine, hexadecylamine and decylamine. If Y is an amido group, possible R1 and/or R2 groups include butynoamido, decynoamido, pentylamido and hexamido. If Y is a hydroxy group, possible R1 and/or R2 groups include decanol, hexanol, pentanol, and alkyl groups that include a hydroxy anywhere along the chain such as, for example, 4-decanol. If Y is a carbonyl or oxo group, possible R1 and/or R2 groups include 2-decanone, 3-decanone, 4-decanone, 2-pentanone, 3-pentanone, 4-pentanone and decanophenone. Y could also be a combination of the above-described functional groups so that R1 or R2 could be a multi-functional moiety such as benzamido.
As described above, R4 and R5 can be hydrogen, alkyl or alkoxy. For example, if R1 or R2 is an aryl or straight-chained alkyl, R4 and R5 are hydrogen. If R1 or R2 is a substituted aryl or a branched alkyl, R4 and R5 are alkyl or alkoxy. The number of carbons in the alkyl or alkoxy for R4 and R5 can vary, but the preferred range is 1 to 16, more preferably 1 to 10.
Preferred groups for R1 and R2 of formula A (the thiophosphorus) are decyl, octyl, nonyl, dodecyl, hexadecyl, undecyl, hexyl, butoxy, pentoxy, decoxy and hexaoxy. Preferred groups for R1 and R2 of formula B (the thiocarbamate) are decyl, octyl, nonyl, dodecyl, hexadecyl, undecyl and hexyl.
R3 of either the thiophosphorus or thiocarbamate additive can be a metallic ion such as molybdenum, tin, antimony, lead, bismuth, nickel, iron, zinc, silver, cadmium or lead and the carbides, oxides, sulfides or oxysulfides thereof. Preferably, R3 is antimony, zinc, cadmium, nickel or molybdenum.
R3 also can be a nonmetallic moiety such as hydrogen, alkyl, alkylaryl, arylalkyl, hydroxyalkyl, oxy-containing group, amido or amino. The alkyl, aryl, alkylaryl, arylalkyl, hydroxyalkyl, or oxy-containing groups could include functional groups such as amino, amido, carboxy or carbonyl.
In general, any alkyl group should be suitable, but alkyls having from 2 to 20, preferably 3 to 16, carbon atoms are preferred. The alkyls could be straight chain or branched. Illustrative alkyl groups include methyl, ethyl, propyl, isopropyl, tert-butyl, pentyl, 2-ethylhexyl, dodecyl, decyl, hexadecyl and octadecyl. In general, any aryl groups should be suitable. Illustrative aryl groups include phenyl, benzylidene, benzoyl and naphthyl. In general, any amido-containing groups should be suitable. Illustrative amido groups include butynoamido, decynoamido, pentylamido and hexamido. In general, any amino groups should be suitable. Illustrative amino groups include butylamine, nonylamine, hexadecylamine and decylamine. In general, any alkylaryl or arylalkyl groups should be suitable. Illustrative alkylaryl or arylalkyls include benzyl, phenylethyl, phenylpropyl, and alkyl-substituted phenyl alcohol. In general, any oxy-containing groups should be suitable, but alkoxy groups having from 2 to 20, preferably 3 to 12, carbon atoms are preferred. Illustrative alkoxy groups include methoxy, ethoxy, propoxy, butoxy and heptoxy.
R3 also can be a divalent group that links together two thiophosphorus or thiocarbamates units to form a dimer. In this instance, subscript x of formula A or B will be 2 and the thiocarbamate additive, for example, will have the following formula: ##STR3##
Possible divalent groups include alkylene. In general, any alkylene groups should be suitable, but those having from 1 to 16, preferably 1 to 8, carbon atoms are preferred. Illustrative alkylene groups include methylene and propylene. A commercially available example of an alkylene thiocarbamate is methylene bis(dibutyldithiocarbamate) available from R. T. Vanderbilt Co. under the tradename Vanlube® 7723.
Subscripts a and b of formulae A or B preferably are both 1. In other words, a dithiophosphorus or ditihocarbamate is the preferred additive.
Particularly preferred dithiophosphorus additives include sulfurized oxymolybdenum organophosphorodithioate available from R. T. Vanderbilt Co. under the tradename Molyvan® L, and antimony dialkylphosphorodithioates available from R. T. Vanderbilt Co. under the tradenames Vanlube® 622 and 648. Particularly preferred dithiocarbamates include molybdenum oxysulfide dithiocarbamate available from R. T. Vanderbilt Co. under the tradename Molyvan® A, organo molybdenum dithiocarbamate available from R. T. Vanderbilt Co. under the tradename Molyvan® 822, zinc diamyldithiocarbamate available from R. T. Vanderbilt Co. under the tradename Molyvan® AZ, lead diamyldithiocarbamate available from R. T. Vanderbilt Co. under the tradename Vanlube® 71, and antimony dialkyldithiocarbamate available from R. T. Vanderbilt Co. under the tradename Vanlube® 73.
The thiophosphorus or thiocarbamate additive that is added to the magnetorheological fluid preferably is in a liquid state at ambient room temperature and does not contain any particles above molecular size.
A mixture of a thiophosphorus additive and a thiocarbamate additive could also be used in a magnetorheological fluid. The thiophosphorus and/or thiocarbamate can be present in an amount of 0.1 to 12, preferably 0.25 to 10, volume percent, based on the total volume of the magnetorheological fluid.
It has also been surprisingly found that an advantageous synergistic effect can be achieved if other additives are included with the thiophosphorus and/or thiocarbamate. Examples of such supplemental or second additives include organomolybdenums, phosphates and sulfur-containing compounds.
The organomolybdenum additive can be a compound or complex whose structure includes at least one molybdenum atom bonded to or coordinated with at least one organic moiety. The organic moiety can be, for example, derived from a saturated or unsaturated hydrocarbon such as alkane, or cycloalkane; an aromatic hydrocarbon such as phenol or thiophenol; an oxygen-containing compound such as carboxylic acid or anhydride, ester, ether, keto or alcohol; a nitrogen-containing compound such as amidine, amine or imine; or a compound containing more than one functional group such as thiocarboxylic acid, imidic acid, thiol, amide, imide, alkoxy or hydroxy amine, and amino-thiol-alcohol. The precursor for the organic moiety can be a monomeric compound, an oligomer or polymer. A heteroatom such as ═O, --S or .tbd.N also can be bonded to or coordinated with the molybdenum atom in addition to the organic moiety.
A particularly preferred group of organomolybdenums is described in U.S. Pat. No. 4,889,647 and U.S. Pat. No. 5,412,130, both incorporated herein by reference. U.S. Pat. No. 4,889,647 describes an organomolybdenum complex that is prepared by reacting a fatty oil, diethanolamine and a molybdenum source. U.S. Pat. No. 5,412,130 describes heterocyclic organomolybdates that are prepared by reacting diol, diamino-thiol-alcohol and amino-alcohol compounds with a molybdenum source in the presence of a phase transfer agent. An organomolybdenum that is prepared according to U.S. Pat. No. 4,889,647 and U.S. Pat. No. 5,412,130 is available from R. T. Vanderbilt Co. under the tradename Molyvan® 855.
Organomolybdenums that also might be useful are described in U.S. Pat. No. 5,137,647 which describes an organomolybdenum that is prepared by reacting an amine-amide with a molybdenum source, U.S. Pat. No. 4,990,271 which describes a molybdenum hexacarbonyl dixanthogen, U.S. Pat. No. 4,164,473 which describes an organomolybdenum that is prepared by reacting a hydrocarbyl substituted hydroxy alkylated amine with a molybdenum source, and U.S. Pat. No. 2,805,997 which describes alkyl esters of molybdic acid.
The organomolybdenum additive that is added to the magnetorheological fluid preferably is in a liquid state at ambient room temperature and does not contain any particles above molecular size.
The organomolybdenum additive can be present in an amount of 0.1 to 12, preferably 0.25 to 10, volume percent, based on the total volume of the magnetorheological fluid.
Useful phosphates include alkyl, aryl, alkylaryl, arylalkyl, amine and alkyl amine phosphates. Illustrative of such phosphates are tricresyl phosphate, trixylenyl phosphate, dilauryl phosphate, octadecyl phosphate, hexadecyl phosphate, dodecyl phosphate and didodecyl phosphate. A particularly preferred alkyl amine phosphate is available from R. T. Vanderbilt Company under the tradename Vanlube® 9123. Examples of sulfur-containing compounds include thioesters such as tetrakis thioglycolate, tetrakis(3-mercaptopropionyl) pentaerithritol, ethylene glycoldimercaptoacetate, 1,2,6-hexanetriol trithioglycolate, trimethylol ethane tri(3-mercaptopropionate), glycoldimercaptopropionate, bisthioglycolate, trimethylolethane trithioglycolate, trimethylolpropane tris(3-mercaptopropionate) and similar compounds and thiols such as 1-dodecylthiol, 1-decanethiol, 1-methyl-1-decanethiol, 2-methyl-2-decanethiol, 1-hexadecylthiol, 2-propyl-2-decanethiol, 1-butylthiol, 2-hexadecylthiol and similar compounds.
The magnetic-responsive particle component of the magnetorheological material of the invention can be comprised of essentially any solid which is known to exhibit magnetorheological activity. Typical magnetic-responsive particle components useful in the present invention are comprised of, for example, paramagnetic, superparamagnetic or ferromagnetic compounds. Superparamagnetic compounds are especially preferred. Specific examples of magnetic-responsive particle components include particles comprised of materials such as iron, iron oxide, iron nitride, iron carbide, carbonyl iron, chromium dioxide, low carbon steel, silicon steel, nickel, cobalt, and mixtures thereof. The iron oxide includes all known pure iron oxides, such as Fe2 O3 and Fe3 O4, as well as those containing small amounts of other elements, such as manganese, zinc or barium. Specific examples of iron oxide include ferrites and magnetites. In addition, the magnetic-responsive particle component can be comprised of any of the known alloys of iron, such as those containing aluminum, silicon, cobalt, nickel, vanadium, molybdenum, chromium, tungsten, manganese and/or copper.
The magnetic-responsive particle component can also be comprised of the specific iron-cobalt and iron-nickel alloys described in U.S. Pat. No. 5,382,373. The iron-cobalt alloys useful in the invention have an iron:cobalt ratio ranging from about 30:70 to 95:5, preferably ranging from about 50:50 to 85:15, while the iron-nickel alloys have an iron:nickel ratio ranging from about 90:10 to 99:1, preferably ranging from about 94:6 to 97:3. The iron alloys may contain a small amount of other elements, such as vanadium, chromium, etc., in order to improve the ductility and mechanical properties of the alloys. These other elements are typically present in an amount that is less than about 3.0% by weight. Due to their ability to generate somewhat higher yield stresses, the iron-cobalt alloys are presently preferred over the iron-nickel alloys for utilization as the particle component in a magnetorheological material. Examples of the preferred iron-cobalt alloys can be commercially obtained under the tradenames HYPERCO (Carpenter Technology), HYPERM (F. Krupp Widiafabrik), SUPERMENDUR (Arnold Eng.) and 2V-PERMENDUR (Western Electric).
The magnetic-responsive particle component of the invention is typically in the form of a metal powder which can be prepared by processes well known to those skilled in the art. Typical methods for the preparation of metal powders include the reduction of metal oxides, grinding or attrition, electrolytic deposition, metal carbonyl decomposition, rapid solidification, or smelt processing. Various metal powders that are commercially available include straight iron powders, reduced iron powders, insulated reduced iron powders, cobalt powders, and various alloy powders such as 48%!Fe/ 50%!Co/ 2%!V powder available from UltraFine Powder Technologies.
The preferred magnetic-responsive particles are those that contain a majority amount of iron in some form. Carbonyl iron powders that are high purity iron particles made by the thermal decomposition of iron pentacarbonyl are particularly preferred. Carbonyl iron of the preferred form is commercially available from ISP Technologies, GAF Corporation and BASF Corporation.
The particle size should be selected so that it exhibits multi-domain characteristics when subjected to a magnetic field. The magnetic-responsive particles should have an average particle size distribution of at least about 0.1 μm, preferably at least about 1 μm. The average particle size distribution should range from about 0.1 to about 500 μm, with from about 1 to about 500 μm being preferred, about 1 to about 250 μm being particularly preferred, and from about 1 to about 100 μm being especially preferred.
The amount of magnetic-responsive particles in the magnetorheological fluid depends upon the desired magnetic activity and viscosity of the fluid, but should be from about 5 to about 50, preferably from about 15 to 40, percent by volume based on the total volume of the magnetorheological fluid.
The carrier component is a fluid that forms the continuous phase of the magnetorheological fluid. Suitable carrier fluids may be found to exist in any of the classes of oils or liquids known to be carrier fluids for magnetorheological fluids such as natural fatty oils, mineral oils, polyphenylethers, dibasic acid esters, neopentylpolyol esters, phosphate esters, polyesters (such as perfluorinated polyesters), synthetic cycloparaffin oils and synthetic paraffin oils, unsaturated hydrocarbon oils, monobasic acid esters, glycol esters and ethers, synthetic hydrocarbon oils, perfluorinated polyethers, and halogenated hydrocarbons, as well as mixtures and derivatives thereof. The carrier component may be a mixture of any of these classes of fluids. The preferred carrier component is non-volatile, non-polar and does not include any significant amount of water. The carrier component (and thus the magnetorheological fluid) particularly preferably should not include any volatile solvents commonly used in lacquers or compositions that are coated onto a surface and then dried such as toluene, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, and acetone. Descriptions of suitable carrier fluids can be found, for example, in U.S. Pat. No. 2,751,352 and U.S. Pat. No. 5,382,373, both hereby incorporated by reference. Hydrocarbons, such as mineral oils, paraffins, cycloparaffins (also known as naphthenic oils) and synthetic hydrocarbons are the preferred classes of carrier fluids. The synthetic hydrocarbon oils include those oils derived from oligomerization of olefins such as polybutenes and oils derived from high alpha olefins of from 8 to 20 carbon atoms by acid catalyzed dimerization and by oligomerization using trialuminum alkyls as catalysts. Such poly-α-olefin oils are particularly preferred carrier fluids. Carrier fluids appropriate to the present invention may be prepared by methods well known in the art and many are commercially available.
The carrier fluid of the present invention is typically utilized in an amount ranging from about 50 to 95, preferably from about 60 to 85, percent by volume of the total magnetorheological fluid.
The magnetorheological fluid can optionally include other additives such as a thixotropic agent, a carboxylate soap, an antioxidant, a lubricant and a viscosity modifier. If present, the amount of these optional additives typically ranges from about 0.25 to about 10, preferably about 0.5 to about 7.5, volume percent based on the total volume of the magnetorheological fluid.
Useful thixotropic agents are described, for example, in WO 94/10693 and commonly-assigned U.S. patent application Ser. No. 08/575,240, incorporated herein by reference. Such thixotropic agents include polymer-modified metal oxides. The polymer-modified metal oxide can be prepared by reacting a metal oxide powder with a polymeric compound that is compatible with the carrier fluid and capable of shielding substantially all of the hydrogen-bonding sites or groups on the surface of the metal oxide from any interaction with other molecules. Illustrative metal oxide powders include precipitated silica gel, fumed or pyrogenic silica, silica gel, titanium dioxide, and iron oxides such as ferrites or magnetites. Examples of polymeric compounds useful in forming the polymer-modified metal oxides include siloxane oligomers, mineral oils and paraffin oils, with siloxane oligomers being preferred. The metal oxide powder may be surface-treated with the polymeric compound through techniques well known to those skilled in the art of surface chemistry. A polymer-modified metal oxide, in the form of fumed silica treated with a siloxane oligomer, can be commercially obtained under the trade names AEROSIL R-202 and CABOSIL TS-720 from DeGussa Corporation and Cabot Corporation, respectively.
Examples of the carboxylate soap include lithium stearate, calcium stearate, aluminum stearate, ferrous oleate, ferrous naphthenate, zinc stearate, sodium stearate, strontium stearate and mixtures thereof.
The viscosity of the magnetorheological fluid is dependent upon the specific use of the magnetorheological fluid. In the instance of a magnetorheological fluid that is used with a damper the carrier fluid should have a viscosity of 6 to 500, preferably 15 to 395, Pa-sec measured at 40° C. in the off-state.
The magnetorheological fluid can be used in any controllable device such as dampers, mounts, clutches, brakes, valves and similar devices. These magnetorheological devices include a housing or chamber that contains the magnetorheological fluid. Such devices are known and are described, for example, in U.S. Pat. No. 5,277,281; U.S. Pat. No. 5,284,330; U.S. Pat. No. 5,398,917; U.S. Pat. Nos. 5,492,312; 5,176,368; 5,257,681; 5,353,839; and 5,460,585, all incorporated herein by reference, and PCT published patent application WO 96/07836. The fluid is particularly suitable for use in devices that require exceptional durability such as dampers. As used herein, "damper" means an apparatus for damping motion between two relatively movable members. Dampers include, but are not limited to, shock absorbers such as automotive shock absorbers. The magnetorheological dampers described in U.S. Pat. No. 5,277,281 and U.S. Pat. No. 5,284,330, both incorporated herein by reference, are illustrative of magnetorheological dampers that could use the magnetorheological fluid.
Examples of the magnetorheological fluid were prepared as follows:
A synthetic hydrocarbon oil derived from poly-α-olefin (available from Albemarle Corp. under the tradename DURASYN 164) was homogeneously mixed with the additives and in the amounts shown in Table 1. To this homogeneous mixture, carbonyl iron (available from GAF Corp. under the tradename R2430) in the amount shown in Table 1 was added while continuing mixing. Fumed silica (available from Cabot Corp. under the tradename CAB-O-SIL TS-720) in the amount shown in Table 1 was then added while continuing mixing. The full formulation then was mixed while cooling with an ice bath to maintain the temperature near ambient. Table 1 shows the composition of the fluids prepared with all quantities in weight percent based on the total weight of the final fluid. In all the fluids the carrier fluid (DURASYN 164) was 70.2 volume %, the carbonyl iron was 25 volume % and the CAB-O-SIL TS-720 was 1.8 volume %.
TABLE 1__________________________________________________________________________ Non-metal Zinc Antimony Organo- Amine- dialkyl- diamyldithio- dialkyl- molybdenum alkylphosphate dithiophosphate carbamate dithiophosphateSample Molyvan 855 Vanlube 9123 Vanlube 7611M Vanlube AZ Vanluble 622__________________________________________________________________________Fluid 1 0 0 3.0 0 0Fluid 2 1.5 0 1.5 0 0Fluid 3 0 0 0 2.51 0.5Fluid 4 0.5 0 0 2.0 0.5Fluid 5 1.0 0 0 1.51 0.5Fluid 6 0 0 0 3.0 0__________________________________________________________________________ 1 An antimony dialkylthiocarbamate (Vanlube ® 73 available from R. T. Vanderbuilt) was substituted for the zinc diamyldithiocarbamate.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2751352 *||23 Aug 1951||19 Jun 1956||Shell Dev||Magnetic fluids|
|US2805997 *||29 Jun 1955||10 Sep 1957||California Research Corp||Lubricant composition|
|US2886151 *||7 Jan 1949||12 May 1959||Wefco Inc||Field responsive fluid couplings|
|US4063000 *||17 Sep 1975||13 Dec 1977||Fuji Photo Film Co., Ltd.||Process for production of ferromagnetic powder|
|US4164473 *||28 Jul 1978||14 Aug 1979||Exxon Research & Engineering Co.||Organo molybdenum friction reducing antiwear additives|
|US4253886 *||8 Aug 1977||3 Mar 1981||Fuji Photo Film Co., Ltd.||Corrosion resistant ferromagnetic metal powders and method of preparing the same|
|US4834898 *||14 Mar 1988||30 May 1989||Board Of Control Of Michigan Technological University||Reagents for magnetizing nonmagnetic materials|
|US4889647 *||14 Nov 1985||26 Dec 1989||R. T. Vanderbilt Company, Inc.||Organic molybdenum complexes|
|US4990271 *||7 Sep 1989||5 Feb 1991||Exxon Research And Engineering Company||Antiwear, antioxidant and friction reducing additive for lubricating oils|
|US5043070 *||13 Nov 1989||27 Aug 1991||Board Of Control Of Michigan Technological University||Magnetic solvent extraction|
|US5094769 *||13 May 1988||10 Mar 1992||International Business Machines Corporation||Compliant thermally conductive compound|
|US5137647 *||9 Dec 1991||11 Aug 1992||R. T. Vanderbilt Company, Inc.||Organic molybdenum complexes|
|US5143637 *||15 Feb 1991||1 Sep 1992||Nippon Seiko Kabushiki Kaisha||Magnetic fluid composition|
|US5213704 *||13 Sep 1991||25 May 1993||International Business Machines Corporation||Process for making a compliant thermally conductive compound|
|US5271858 *||2 Oct 1992||21 Dec 1993||Ensci Inc.||Field dependent fluids containing electrically conductive tin oxide coated materials|
|US5382373 *||30 Oct 1992||17 Jan 1995||Lord Corporation||Magnetorheological materials based on alloy particles|
|US5412130 *||8 Jun 1994||2 May 1995||R. T. Vanderbilt Company, Inc.||Method for preparation of organic molybdenum compounds|
|WO1994010692A1 *||12 Oct 1993||11 May 1994||Lord Corp||Low viscosity magnetorheological materials|
|WO1994010693A1 *||18 Oct 1993||11 May 1994||Lord Corp||Thixotropic magnetorheological materials|
|WO1994010694A1 *||27 Oct 1993||11 May 1994||Lord Corp||Magnetorheological materials utilizing surface-modified particles|
|1||"Vanderbilt Lubricant Additives" R.T. Vanderbilt Company, Inc.; Technical Bulletin No. 941; Jun. 1994.|
|2||*||(Derwent Abstract) DD A 296574 Jul. 4, 1990.|
|3||(Derwent Abstract) DD A -296574 Jul. 4, 1990.|
|4||*||Japan (Derwent Abstract) JP A 62 195729 Aug. 28, 1987.|
|5||Japan (Derwent Abstract) JP A -62-195729 Aug. 28, 1987.|
|6||*||Japan JP B 89 021202 Apr. 20, 1989.|
|7||Japan JP B -89-021202 Apr. 20, 1989.|
|8||*||Vanderbilt Lubricant Additives R.T. Vanderbilt Company, Inc.; Technical Bulletin No. 941; Jun. 1994.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US6168634||25 Mar 1999||2 Jan 2001||Geoffrey W. Schmitz||Hydraulically energized magnetorheological replicant muscle tissue and a system and a method for using and controlling same|
|US6234060||8 Mar 1999||22 May 2001||Lord Corporation||Controllable pneumatic apparatus including a rotary-acting brake with field responsive medium and control method therefor|
|US6302249||8 Mar 1999||16 Oct 2001||Lord Corporation||Linear-acting controllable pneumatic actuator and motion control apparatus including a field responsive medium and control method therefor|
|US6395193||3 May 2000||28 May 2002||Lord Corporation||Magnetorheological compositions|
|US6475404||3 May 2000||5 Nov 2002||Lord Corporation||Instant magnetorheological fluid mix|
|US6527972||20 Feb 2001||4 Mar 2003||The Board Of Regents Of The University And Community College System Of Nevada||Magnetorheological polymer gels|
|US6547983||14 Dec 2000||15 Apr 2003||Delphi Technologies, Inc.||Durable magnetorheological fluid compositions|
|US6599439||14 Dec 2000||29 Jul 2003||Delphi Technologies, Inc.||Durable magnetorheological fluid compositions|
|US6638443||21 Sep 2001||28 Oct 2003||Delphi Technologies, Inc.||Optimized synthetic base liquid for magnetorheological fluid formulations|
|US6764520||22 Jan 2001||20 Jul 2004||Massachusetts Institute Of Technology||Electronically controlled prosthetic knee|
|US6818143||29 Jan 2003||16 Nov 2004||Delphi Technologies, Inc.||Durable magnetorheological fluid|
|US6871553||28 Mar 2003||29 Mar 2005||Delphi Technologies, Inc.||Integrating fluxgate for magnetostrictive torque sensors|
|US6872427||7 Feb 2003||29 Mar 2005||Delphi Technologies, Inc.||Method for producing electrical contacts using selective melting and a low pressure kinetic spray process|
|US6881353 *||15 Sep 2003||19 Apr 2005||General Motors Corporation||Magnetorheological fluids with stearate and thiophosphate additives|
|US6886819 *||6 Nov 2002||3 May 2005||Lord Corporation||MR fluid for increasing the output of a magnetorheological fluid damper|
|US6924249||2 Oct 2002||2 Aug 2005||Delphi Technologies, Inc.||Direct application of catalysts to substrates via a thermal spray process for treatment of the atmosphere|
|US6949300||16 Apr 2003||27 Sep 2005||Delphi Technologies, Inc.||Product and method of brazing using kinetic sprayed coatings|
|US7001671||1 Oct 2003||21 Feb 2006||Delphi Technologies, Inc.||Kinetic sprayed electrical contacts on conductive substrates|
|US7024946||23 Jan 2004||11 Apr 2006||Delphi Technologies, Inc.||Assembly for measuring movement of and a torque applied to a shaft|
|US7070707||23 May 2002||4 Jul 2006||Lord Corporation||Magnetorheological composition|
|US7070708||30 Apr 2004||4 Jul 2006||Delphi Technologies, Inc.||Magnetorheological fluid resistant to settling in natural rubber devices|
|US7101487||25 Nov 2003||5 Sep 2006||Ossur Engineering, Inc.||Magnetorheological fluid compositions and prosthetic knees utilizing same|
|US7108893||9 Jul 2003||19 Sep 2006||Delphi Technologies, Inc.||Spray system with combined kinetic spray and thermal spray ability|
|US7198071||6 May 2005||3 Apr 2007||Össur Engineering, Inc.||Systems and methods of loading fluid in a prosthetic knee|
|US7198137||29 Jul 2004||3 Apr 2007||Immersion Corporation||Systems and methods for providing haptic feedback with position sensing|
|US7217372||1 Nov 2002||15 May 2007||Lord Corporation||Magnetorheological composition|
|US7279009||22 Aug 2003||9 Oct 2007||Massachusetts Institute Of Technology||Speed-adaptive and patient-adaptive prosthetic knee|
|US7335233||15 Mar 2006||26 Feb 2008||Ossur Hf||Magnetorheological fluid compositions and prosthetic knees utilizing same|
|US7335341||30 Oct 2003||26 Feb 2008||Delphi Technologies, Inc.||Method for securing ceramic structures and forming electrical connections on the same|
|US7351450||2 Oct 2003||1 Apr 2008||Delphi Technologies, Inc.||Correcting defective kinetically sprayed surfaces|
|US7445094||11 Oct 2005||4 Nov 2008||The United States Of America As Represented By The Secretary Of The Air Force||Passive magneto-rheological vibration isolation apparatus|
|US7455696||6 May 2005||25 Nov 2008||össur hf||Dynamic seals for a prosthetic knee|
|US7475831||23 Jan 2004||13 Jan 2009||Delphi Technologies, Inc.||Modified high efficiency kinetic spray nozzle|
|US7476422||23 May 2002||13 Jan 2009||Delphi Technologies, Inc.||Copper circuit formed by kinetic spray|
|US7511084||4 Feb 2003||31 Mar 2009||Basf Aktiengesellschaft||Acyl- and bisacylphosphine derivatives|
|US7522152||27 May 2004||21 Apr 2009||Immersion Corporation||Products and processes for providing haptic feedback in resistive interface devices|
|US7556140||15 Aug 2007||7 Jul 2009||Martin Engineering Company||Bulk material handling system|
|US7567243||1 Jun 2004||28 Jul 2009||Immersion Corporation||System and method for low power haptic feedback|
|US7575695||17 Jan 2007||18 Aug 2009||Delphi Technologies, Inc.||Additives package and magnetorheological fluid formulations for extended durability|
|US7628254||19 Sep 2008||8 Dec 2009||The United States Of America As Represented By The Secretary Of The Air Force||Passive magneto-rheological vibration isolation apparatus using a shielding sleeve|
|US7669708||15 Aug 2007||2 Mar 2010||Martin Engineering Company||Bulk material handling system and control|
|US7674076||14 Jul 2006||9 Mar 2010||F. W. Gartner Thermal Spraying, Ltd.||Feeder apparatus for controlled supply of feedstock|
|US7691154||6 May 2005||6 Apr 2010||össur hf||Systems and methods of controlling pressure within a prosthetic knee|
|US7740126||3 Dec 2008||22 Jun 2010||Martin Engineering Company||Bulk material handling system|
|US7740127||3 Dec 2008||22 Jun 2010||Martin Engineering Company||Bulk material handling system|
|US7764268||24 Sep 2004||27 Jul 2010||Immersion Corporation||Systems and methods for providing a haptic device|
|US7775341||3 Dec 2008||17 Aug 2010||Martin Engineering Company||Bulk material handling system|
|US7799091||8 Oct 2007||21 Sep 2010||Massachusetts Institute Of Technology||Control system for prosthetic knee|
|US7959822||29 Jun 2006||14 Jun 2011||Basf Se||Magnetorheological liquid|
|US8002089||10 Sep 2004||23 Aug 2011||Immersion Corporation||Systems and methods for providing a haptic device|
|US8013847||24 Aug 2004||6 Sep 2011||Immersion Corporation||Magnetic actuator for providing haptic feedback|
|US8018434||26 Jul 2010||13 Sep 2011||Immersion Corporation||Systems and methods for providing a haptic device|
|US8037997||3 Dec 2008||18 Oct 2011||Martin Engineering Company||Bulk material handling system and control|
|US8057550||23 Mar 2009||15 Nov 2011||össur hf.||Transfemoral prosthetic systems and methods for operating the same|
|US8069971||3 Dec 2008||6 Dec 2011||Martin Engineering Company||Bulk material handling system and control|
|US8154512||20 Apr 2009||10 Apr 2012||Immersion Coporation||Products and processes for providing haptic feedback in resistive interface devices|
|US8205741||6 Aug 2010||26 Jun 2012||Martin Engineering Company||Method of adjusting conveyor belt scrapers and open loop control system for conveyor belt scrapers|
|US8248363||24 Oct 2007||21 Aug 2012||Immersion Corporation||System and method for providing passive haptic feedback|
|US8323354||30 Mar 2012||4 Dec 2012||Victhom Human Bionics Inc.||Instrumented prosthetic foot|
|US8441433||11 Aug 2004||14 May 2013||Immersion Corporation||Systems and methods for providing friction in a haptic feedback device|
|US8486292||18 Sep 2007||16 Jul 2013||Basf Se||Magnetorheological formulation|
|US8617254||22 Jan 2010||31 Dec 2013||Ossur Hf||Control system and method for a prosthetic knee|
|US8619031||27 Jul 2009||31 Dec 2013||Immersion Corporation||System and method for low power haptic feedback|
|US8657886||16 Jun 2011||25 Feb 2014||össur hf||Systems and methods for actuating a prosthetic ankle|
|US8702811||19 Apr 2012||22 Apr 2014||össur hf||System and method for determining terrain transitions|
|US8801802||15 Feb 2006||12 Aug 2014||össur hf||System and method for data communication with a mechatronic device|
|US8803796||26 Aug 2004||12 Aug 2014||Immersion Corporation||Products and processes for providing haptic feedback in a user interface|
|US8814949||18 Apr 2006||26 Aug 2014||össur hf||Combined active and passive leg prosthesis system and a method for performing a movement with such a system|
|US8852292||30 Aug 2006||7 Oct 2014||Ossur Hf||System and method for determining terrain transitions|
|US8986397||19 Jan 2012||24 Mar 2015||Victhom Human Bionics, Inc.||Instrumented prosthetic foot|
|US9046922||20 Sep 2004||2 Jun 2015||Immersion Corporation||Products and processes for providing multimodal feedback in a user interface device|
|US9066819||18 Mar 2013||30 Jun 2015||össur hf||Combined active and passive leg prosthesis system and a method for performing a movement with such a system|
|US9078774||12 Aug 2010||14 Jul 2015||össur hf||Systems and methods for processing limb motion|
|US20030209687 *||29 Jan 2003||13 Nov 2003||Iyengar Vardarajan R.||Durable magnetorheological fluid|
|US20040039454 *||22 Aug 2003||26 Feb 2004||Herr Hugh M.||Speed-adaptive and patient-adaptive prosthetic knee|
|US20040058065 *||9 Jul 2003||25 Mar 2004||Steenkiste Thomas Hubert Van||Spray system with combined kinetic spray and thermal spray ability|
|US20040065391 *||2 Oct 2002||8 Apr 2004||Smith John R||Direct application of catalysts to substrates via a thermal spray process for treatment of the atmosphere|
|US20040065432 *||2 Oct 2002||8 Apr 2004||Smith John R.||High performance thermal stack for electrical components|
|US20040072008 *||1 Oct 2003||15 Apr 2004||Delphi Technologies, Inc.||Kinetic sprayed electrical contacts on conductive substrates|
|US20040084263 *||6 Nov 2002||6 May 2004||Lord Corporation||MR device|
|US20040101620 *||22 Nov 2002||27 May 2004||Elmoursi Alaa A.||Method for aluminum metalization of ceramics for power electronics applications|
|US20040135115 *||17 Jun 2003||15 Jul 2004||General Motors Corporation||Magnetorheological fluids with stearate and thiophosphate additives|
|US20040142198 *||21 Jan 2003||22 Jul 2004||Thomas Hubert Van Steenkiste||Magnetostrictive/magnetic material for use in torque sensors|
|US20040149953 *||15 Sep 2003||5 Aug 2004||Ulicny John C.||Magnetorheological fluids with stearate and thiophosphate additives|
|US20040157000 *||7 Feb 2003||12 Aug 2004||Steenkiste Thomas Hubert Van||Method for producing electrical contacts using selective melting and a low pressure kinetic spray process|
|US20040217324 *||25 Nov 2003||4 Nov 2004||Henry Hsu||Magnetorheological fluid compositions and prosthetic knees utilizing same|
|US20050040260 *||21 Aug 2003||24 Feb 2005||Zhibo Zhao||Coaxial low pressure injection method and a gas collimator for a kinetic spray nozzle|
|US20050074560 *||2 Oct 2003||7 Apr 2005||Fuller Brian K.||Correcting defective kinetically sprayed surfaces|
|US20050100489 *||30 Oct 2003||12 May 2005||Steenkiste Thomas H.V.||Method for securing ceramic structures and forming electrical connections on the same|
|US20050103126 *||21 Dec 2004||19 May 2005||Delphi Technologies, Inc.||Integrating fluxgate for magnetostrictive torque sensors|
|US20050160834 *||23 Jan 2004||28 Jul 2005||Nehl Thomas W.||Assembly for measuring movement of and a torque applied to a shaft|
|US20050161532 *||23 Jan 2004||28 Jul 2005||Steenkiste Thomas H.V.||Modified high efficiency kinetic spray nozzle|
|US20050214474 *||24 Mar 2004||29 Sep 2005||Taeyoung Han||Kinetic spray nozzle system design|
|US20050222294 *||4 Feb 2003||6 Oct 2005||Ralf Noe||Acyl- and bisacylphosphine derivatives|
|US20050242321 *||30 Apr 2004||3 Nov 2005||Delphi Technologies, Inc.||Magnetorheological fluid resistant to settling in natural rubber devices|
|US20060038044 *||23 Aug 2004||23 Feb 2006||Van Steenkiste Thomas H||Replaceable throat insert for a kinetic spray nozzle|
|US20060040048 *||23 Aug 2004||23 Feb 2006||Taeyoung Han||Continuous in-line manufacturing process for high speed coating deposition via a kinetic spray process|
|US20060178753 *||15 Mar 2006||10 Aug 2006||Henry Hsu||Magnetorheological fluid compositions and prosthetic knees utilizing same|
|US20060197051 *||3 May 2006||7 Sep 2006||Henry Hsu||Magnetorheological fluid compositions and prosthetic knees utilizing same|
|US20060251823 *||7 Jul 2006||9 Nov 2006||Delphi Corporation||Kinetic spray application of coatings onto covered materials|
|US20070074656 *||4 Oct 2005||5 Apr 2007||Zhibo Zhao||Non-clogging powder injector for a kinetic spray nozzle system|
|US20070170392 *||17 Jan 2007||26 Jul 2007||Delphi Technologies, Inc.||Additives package and magnetorheological fluid formulations for extended durability|
|US20080014031 *||14 Jul 2006||17 Jan 2008||Thomas Hubert Van Steenkiste||Feeder apparatus for controlled supply of feedstock|
|US20080053791 *||15 Aug 2007||6 Mar 2008||Swinderman R Todd||Bulk Material Handling System and Control|
|US20080053792 *||15 Aug 2007||6 Mar 2008||Swinderman R Todd||Bulk Material Handling System|
|US20090078536 *||3 Dec 2008||26 Mar 2009||Martin Engineering Company||Bulk Material Handling System|
|US20090078538 *||3 Dec 2008||26 Mar 2009||Martin Engineering Company||Bulk Material Handling System|
|US20090078539 *||3 Dec 2008||26 Mar 2009||Martin Engineering Company||Bulk Material Handling System|
|US20090082904 *||3 Dec 2008||26 Mar 2009||Martin Engineering Company||Bulk Material Handling System and Control|
|US20090289214 *||18 Sep 2007||26 Nov 2009||Basf Se||Magnetorheological formulation|
|US20090294252 *||3 Dec 2009||Martin Engineering Company||Bulk Material Handling System and Control|
|US20100078586 *||29 Jun 2006||1 Apr 2010||Basf Aktiengesellschaft||Magnetorheological liquid|
|US20100155649 *||4 Mar 2010||24 Jun 2010||The University Of Akron||Molecule-based magnetic polymers and methods|
|USRE39961||29 Apr 2003||25 Dec 2007||össur hf||Computer controlled hydraulic resistance device for a prosthesis and other apparatus|
|USRE42903||20 Jul 2006||8 Nov 2011||Massachusetts Institute Of Technology||Electronically controlled prosthetic knee|
|DE19852152A1 *||4 Nov 1998||18 May 2000||Mediport Kardiotechnik Gmbh||Magnetische Teilchen, magnetische Dispersionen und Verfahren zu ihrer Herstellung|
|DE19852152C2 *||4 Nov 1998||26 Sep 2002||Berlin Heart Ag||Magnetische Teilchen, deren Herstellung und Verfahren zur Herstellung magnetischer Dispersionen davon|
|EP1283532A2 *||5 Aug 2002||12 Feb 2003||General Motors Corporation||Magnetorheological fluids with stearate and thiophosphate additives|
|EP1283532A3 *||5 Aug 2002||13 Aug 2003||General Motors Corporation||Magnetorheological fluids with stearate and thiophosphate additives|
|EP1423859A1 *||3 Sep 2002||2 Jun 2004||Behr America, Inc||Magnetorheological fluids with an additive package|
|EP1492133A1 *||16 Jun 2004||29 Dec 2004||General Motors Corporation||Magnetorheological fluids with stearate and thiophosphate additives|
|EP1811529A1 *||18 Jan 2007||25 Jul 2007||Delphi Technologies, Inc.||Additives package and magnetorheological fluid formulations for extended durability|
|EP1918944A2 *||26 Oct 2007||7 May 2008||Repsol Ypf S.A.||Magnetorheological Fluid (MRF)|
|WO2000053936A1||2 Mar 2000||14 Sep 2000||Lord Corp||Controllable pneumatic apparatus including a rotary-acting brake with field responsive medium and control method therefor|
|WO2000053937A1||2 Mar 2000||14 Sep 2000||Lord Corp||Linear-acting controllable pneumatic actuator and motion control apparatus including a field responsive medium and control method therefor|
|WO2004044931A2 *||6 Nov 2003||27 May 2004||Lord Corp||Improved mr device|
|WO2012106597A1||3 Feb 2012||9 Aug 2012||Lord Corporation||Polyols and their use in hydrocarbon lubricating and drilling fluids|
|U.S. Classification||252/62.52, 252/62.54|
|15 Aug 1996||AS||Assignment|
Owner name: LORD CORPORATION, NORTH CAROLINA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MUNOZ, BETH C.;REEL/FRAME:008091/0079
Effective date: 19960809
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Year of fee payment: 4
|25 Apr 2005||FPAY||Fee payment|
Year of fee payment: 8
|27 Feb 2009||FPAY||Fee payment|
Year of fee payment: 12